I. Field of the Invention
The present disclosure relates generally to the fields of chemistry and materials science. More particularly, it concerns metal-organic frameworks, compositions thereof and methods use thereof, including for storing, detecting, and separating of gas and/or liquid molecules.
II. Description of Related Art
Microporous metal-organic frameworks (MOFs) have been rapidly emerging as new type of porous materials for gas storage, separation, sensing and heterogeneous catalysis. The tunable pores and the immobilized functional sites within such microporous MOFs have enabled them to direct specific recognition of certain molecules, and thus for their highly selective guest sorption and separation. The diverse metal ions and/or metal-containing clusters as the nodes and a variety of organic linkers as the bridges to construct the porous coordination polymers (PCPs) by the coordination bonds have led to a series of porous MOFs from ultramicroporous to mesoporous domains. Although thousands of MOFs have been synthesized and structurally characterized over the past two decades, those exhibiting permanent porosity and thus being classified as porous MOFs are still of few percentage. This is primarily due to the labile coordination geometries of the metal ions and/or metal-containing clusters, and the flexibility of the bridging organic linkers which cannot sustain the frameworks under vacuum and/or thermal activation. One efficient strategy to stabilize the PCPs and thus to construct porous MOFs is to make use of rigid clusters (Fang et al., 2006a; Fang et al., 2006b; Bai et al., 2008; Wang et al., 2009), as exemplified in those MOFs with the binuclear paddle-wheel M2(COO)6 (M=Cu2+, Co2+, Ni2+ and Zn2+) and tetranuclear Zn4O(COO)6 as the secondary building units (Eddaoudi et al., 2000). Another strategy to stabilize the frameworks is to make use of the framework interpenetration and/or interwoven to enforce the framework interactions (Ma and Lin, 2009; Kesanli et al., 2005). This approach has been successful in constructing interpenetrated MOFs with higher permanent porosity than their non-interpenetrated analogues (Ma et al., 2007; Ma et al., 2008).
Although thousands of MOFs have been synthesized and structurally characterized over the past two decades, the ones with open metal sites are still relatively few (Chen et al., 2010; Dinca and Long, 2008), this is mainly because such open metal sites are typically very reactive and tend to bind the atoms from the neighboring ligands to form the condensed structures. Also, few MOFs have been shown to be useful for selective sorption, separation and/or sensing of guest molecules. Accordingly, identifying and developing materials and compositions that exhibit one or more of these useful properties is desirable.